1992 Lumina Problem(s)

I bought my 1992 lumina (with a 3.1L, 4t60 trans, and 120K) with the problem that after the car warmed up it would die. The car sat for like 2 yrs before i found it. I figured out that it was either the Crank Position Sensor or the ICM. I replaced the wrong one first. So then it starts up runs and fine down the road. Until you get to a stop sign. Then once you stop and try to move again it doesn't want to. It revs up like the transmission is slipping or staring in the wrong gear. So i took to a transmission shop and they said it needed rebuilt. Being the cheap person i am i took it to another transmission shop to see if they thought the transmission needed rebuilt and if so the price. They too said it needed rebuilt. But i found that i could get a Transmission with 83K on it for alot less than it would take to rebuild one. I didn't want to put more money into the transmission than i have in the car. I get the transmission installed still the same problem though. And now there is a new problem; When i first start the car up the idle is a little high and when i give gas the RPM's fall like a rock and then go where they should be. When i let off it returns to its high idle. Also when this is happening if i put it in drive or reverse the car will try to move but then the motor will just rev. But after about ten minutes of sitting and idleing everything will work fine. I have checked the vacuum at the modulator with a guage and, according to my manual i have for it, it is in the normal operating range, but when i hit the gas the vacuum also falls like a rock to about 3 mmHG instead of the 15 it was running before. Is That normal. The manual is very vague on how the vacuum should act. The guy i bought it off of said that his garage had replaced a chip in the computer twice. I don't know how reliable or important that information is.
I have replaced the following things
1. ICM
2. Crank position Sensor
3. Plugs and plug wires
4. Transmission
Any help is appreciated. Thank you for your time.

Adam

The vacuum drop is normal. You should have around 15in at idle, and almost none at WOT (Wide Open Throttle). When you replaced the trans, did you replace the torque converter too? It sounds like a bad torque converter to me. Also when replacing a trans like that, it's a good idea to flush the cooler and lines to prevent old grenaded tranny particles from getting in your replacement trans. The idle jumping around sounds like a vacuum leak or sticking IAC valve.

before you spend any more money on parts, it might not be a bad idea to have the ecm reset. On these older lumina's if the battery is disconnected for more than 15minutes you may need to reprogram your idle. When the transmission was being replaced, obviously the battery was removed. There are ways to reprogram the ecm yourself, but it only costs 1/2 an hour's labor at a GM garage, and you know it's done right. The symptoms you are reporting sound exactly to this problem. So, might not be a bad idea.